Wednesday, 22 September 2010

Jurassic Bark


Towards the end of February a spring-like spell of weather meant that conditions at Quarry 4 were rapidly improving and it was obvious that the quarry floor would be drying out. It was time for a return visit.

Mark and I made quick arrangements and we were soon heading to the quarry on a bright Saturday morning. When we arrived the first topic of discussion was what to wear. We went for the compromise which involved mainly spring clothing with a sweater thrown in for good measure. It turned out to be a good decision.

The quarry itself had really dried out although there were still significant pools of water. The clay was really bright grey as opposed to the dark wet grey it was on our last visit. On the horizon we could see a great swathe of clay had been removed at the back of the quarry. We moved off to prospect.

This time the walk through the quarry was much easier. There were still some areas of soft clay to negotiate but now it was much firmer underfoot overall. As we approached the new scrape we came across a newly dug trench, perhaps 150 yards in length and we both dropped into it just about central to its total length. We both started to prospect – I went one way and Mark went the other.

It was much easier to discern this time and the trench looked good. However, the more I looked, the more I realised that this trench was obviously not in a very fossiliferous part of the quarry. This is something that we have now come to realise that, despite its apparent uniformity, Bed 10 can be remarkably zonal. Some parts have mainly belemnites, some are mainly Gryphea (although this is probably due to the fact that Bed 9 intersects now and then), and the best are a mixture of everything. All are dominated by the ammonite Kosmoceras.

But this trench was sparse except every now and then there would be huge blocks of mud shales that were like leaves of a book. All the layers are ultra thin but they all contain beautiful impressions of ammonites and bivalves. Their fragility makes them impossible to collect no matter how careful you try to be. Even if you managed to pick one up you would be certain to destroy them in transit, they are that fragile.

We met up and decided to move to the new scraping. To reach it we had to climb up an awkward spoil heap on the other side of the trench. As we reached the top we looked at each other, smiled and looked below us. The new scraping looked absolutely perfect, level and smack bang on Bed 10. As Mark said “If we don’t find anything here we want our butts kicking”. I knew what he meant.

We immediately began to prospect. Just where we entered the new scraping the digger had obviously gone a little deeper than intended and huge blocks of clay were upended and this was where we started. This was the first time in this quarry that I felt really at home and with the sun beating down on us, and the first warm temperatures for more than 5 months, we just had to find something.

After our initial excitement died down we looked intensively for any sign of bone that would lead to our first significant discovery of the year. This was the first time that we had the advantage of scouring a new face and we were intent on succeeding.

After about an hour we still had nothing to show for our efforts and we started to spread out a little bit more but still maintained our very slow, deliberate and methodical search for fossil bone. Eventually I came to a slight depression and noticed a high concentration of carbonised wood fragments covering a large area.

At the Bluff, wood and bone often go together, so I decided to spend some time here and began carefully scraping at the clay. I soon uncovered what I thought was an unusually large piece of wood and it appeared fairly solid. I began to brush away the clay from one end and the piece got bigger. So I brushed more clay away from the other end and still it got bigger. I called Mark for help.


As we uncovered more of the wood we both realised we had uncovered a really unusual fossil for these marine sediments. There, lying before us was a tree trunk, nearly 3 metres long and quite obviously part of a big tree. I know that you cannot compare it with some of the big trunks in, for instance, Arizona but never the less this was a big piece of wood.

Mark initially thought it may be a species of cypress. Personally, trees aren’t my strongpoint so I didn’t have a clue as to what it was. The immediate question was that now we had uncovered it, what on earth were we going to do with it? It was far too big for either of us to have and, besides, we would need the help of an excavator to remove it.

Eventually we decided to cover it over and mark the spot with a few rocks. Then we would later notify the local museum and see if they would be interested in taking it out. This particular museum had recovered many complete and partial skeletons from this quarry and others like it the area for many years and were very experienced and we felt that they would have the best chance of removing it – if it were required.

We carried on with our search but it became apparent that, despite the ideal conditions and situation, we were doomed to failure again. We both tried hard and I can honestly say that we covered the area with the proverbial fine tooth comb, methodically prospecting as we went. We were both certain that there was nothing to find and abandoned the new scrape for pastures new.

We carried on the search for some time afterward, concentrating our efforts in areas that were underwater from the previous trip but still there were no bones to be found. Quarry 4 and I just haven’t reached a compromise yet – but we will.

We eventually called it a day and walked back to the cars, boneless but in good spirits and, as usual, vowed that it would be our turn next time. I knew that, because of other commitments, it would be most likely May before we returned and, before then, a trip to Misty Bluff was next on the list. But return we would and try yet again to find that elusive marine reptile.

Footnote

A small group from the museum were going into Quarry 4 only 48 hours after our visit to see if the tree could be removed and conserved satisfactorily. They decided it wasn’t really suitable for preservation – besides, they said, where on earth would they put it? Understandable - but still a shame.

We uncovered a tree that hadn’t seen the light of day for 160 million years. When I next returned, it had disintegrated and the last remnants were blowing away in the wind…………

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